R. Bensraj

Comparative study on various bipolar hybrid carrier PWM strategies for three phase five level cascaded inverter

This work presents the comparison of hybrid carrier Pulse Width Modulation (PWM) techniques for the chosen three phase Cascaded Multi Level Inverter (CMLI). In this paper, a CMLI is controlled with Sinusoidal PWM technique with Alternative Phase Opposition and Disposition and Carrier Overlapping (APOD + CO), Alternative Phase Opposition and Disposition and Phase Shift (APOD + PS), Alternative Phase Opposition and Disposition and Variable Frequency (APOD + VF), CO + VF, CO + PS, Phase Disposition and Variable Frequency (PD + VF), PS + PD, PS + VF , APOD + PD and CO + PD and the variation of Total Harmonic Distortion (THD) in the outputs is observed for various modulation indices ma. Simulation is performed using MATLAB-SIMULINK. It is seen that sinusoidal reference with PS+PD provides output with relatively low distortion. CO+VF PWM strategy is found to perform better since it provides relatively higher fundamental RMS output voltage and relatively lower stress on the devices.

Performance evaluation of unipolar PWM strategies for three phase five level diode clamped inverter

This paper presents the comparison of unipolar Pulse Width Modulation techniques for a Diode Clamped Multi Level Inverter (DCMLI). In this paper, the DCMLI is controlled with Sinusoidal PWM (SPWM) reference and Third Harmonic Injection (THI) PWM reference with Sub Harmonic PWM (SHPWM), Carrier Overlapping (CO) PWM, Phase Shift (PS) PWM, Variable Frequency (VF) PWM and the variation of Total Harmonic Distortion (THD) in their outputs is observed for various modulation indices. Simulation is performed using MATLAB-SIMULINK. It is observed that SHPWM strategy provides output with relatively low distortion. It is also noticed that COPWM strategy is found to perform better since it provides relatively higher fundamental RMS output voltage.

Development of Concatenative Syllable-Based Text to Speech Synthesis System for Tamil

This paper addresses the problem of improving the intelligibility of the synthesized speech in Tamil text-to-speech (TTS) synthesis system. The human speech is artificially generated by speech synthesis. The normal language text will be automatically converted into speech using TTS system. This paper deals with a corpus-driven Tamil TTS system based on the concatenative synthesis approach. Concatenative speech synthesis involves the concatenation of the basic units to synthesize an intelligent, natural sounding speech. In this paper, syllables are the basic unit of speech synthesis database and the modification of syllable pitch by timescale modification. The speech units are annotated with associated prosodic information about each unit, manually or automatically, based on an algorithm. An annotated speech corpus utilizes the clustering technique that provides way to select the suitable unit for concatenation, depending on the minimum total joint cost of the speech unit. The entered text file is analyzed first, this syllabication is performed based on the linguistics rules, and the syllables are stored separately. Then, the syllable corresponding speech file is concatenated and the silence present in the concatenated speech is removed. After that, discontinuities are minimized at syllable boundaries without degrading the quality. Smoothing at the concatenated syllable boundary is performed, changing the syllable pitches by timescale modification.

Impact of Variable Bit Rate and Packet Size on the Performance Evaluation of Neighbor Aware AODV and DSDV Routing Protocols for MANET's

Mobile Ad hoc Networks (MANET) have become an exciting and important technology in recent years because of the rapid proliferation of wireless nodes. They consist of wireless host that can move freely, rapidly changing, which are likely composed of relatively limited bandwidth and low powered wireless links. MANET is a wireless mobile network in which mobile nodes can transmit and receive without any fixed infrastructure and can be distributed for many applications such as soldiers relaying critical information, business associates sharing information during get together. Authentic and efficient routing is significant and vital in those benefits. A major dispute that lies in MANET communication is the limit less mobility and more frequent link failures. Conventional routing algorithms are therefore deficient for ad-hoc networks. In this paper we propose a modified approach based on the AODV [2] which affords more beneficial results when compared with the conventional AODV and DSDV protocols. Simulations are accomplished in ns-2 and various performance metrics like throughput, end to end delay, Packet loss and pdr [5,6,8] with variable bit rate, packet size and node density and pause time are computed.

Bipolar trapezoidal amalagated rectangular reference function for improved performance PWM multilevel inverter

In many research papers modulation techniques have been carried out with different techniques but this paper reveals a new idea to enhance the performance of MultiLevel Inverter (MLI). If trapezoidal as a reference in that case 3rd harmonics produces significant spectrum harmonic energy, the impact of that the difficulty arises for filter design. An amalgamated rectangular references is developed to improve the performances of a five level Cascaded MultiLevel Inverter (CMLI). To validate the improvement a MATLAB-SIMULINK based simulation to bipolar amalgamated rectangular reference function is simulated for carrier disposition techniques Phase Shift techniques, Carrier Overlapping technique and Variable Frequency techniques are carried out. FFT analysis and performance of evaluation have been carried out. The simulation results validating the strategies presented. Among the all strategies developed carrier overlapping technique provides relatively higher DC bus utilization and PS provides the lowest distortion for moderate ma.

Comparative Study on Carrier Overlapping PWM Strategies for Three Phase Five Level Cascaded Inverter

paper presents the comparison of Carrier Overlapping Pulse Width Modulation (COPWM) techniques for the Cascaded Multi Level Inverter (CMLI). A CMLI is controlled in this paper with Sinusoidal PWM (SPWM) reference, Third Harmonic Injection PWM (THI PWM) reference, Sixty degree PWM reference and Stepped wave reference with Carrier Overlapping (CO) techniques. The variation of Total Harmonic Distortion (THD) in the inverter output voltage is observed when the chosen inverter is controlled by SPWM for various modulation indices. Simulation is performed using MATLAB-SIMULINK. It is observed that COPWM-C provides output with relatively low distortion for all strategies. It is also seen that COPWM-A is found to perform better for all strategies since it provides relatively higher fundamental RMS output voltage and in particular highest output is obtained for 60 degree PWM reference. KeywordsCMLI, Stepped, THIPWM, 60 degree PWM, COPWM.

Investigations on Three Phase Five Level Cascaded type FCMLI

This work presents the comparison of various multicarrier based Pulse Width Modulation (PWM) techniques for the chosen Hbridge type Flying Capacitor Multi Level Inverter (FCMLI). In this paper, a H-bridge type FCMLI is controlled with Sinusoidal PWM (SPWM) technique with Phase Disposition (PD), Phase Opposition and Disposition (POD), Alternative Opposition and Disposition (APOD), Carrier Overlapping (CO), Phase Shift (PS) and Variable Frequency (VF) PWM techniques and the variation of Total Harmonic Distortion (THD) in the output is observed by varying the modulation index. Simulation is performed using MATLAB-SIMULINK. It is observed that sinusoidal reference with PSPWM provides output with relatively low distortion and relatively lower stress on the devices. It is also seen that COPWM strategy is found to perform better since it provides relatively higher fundamental RMS output voltage and relatively lower stress on the devices.

Unipolar PWM using Trapezoidal Amalgamated Rectangular Reference Function for Improved Performance of Multilevel Inverter

In many research papers, Pulse Width Modulation (PWM) techniques have been carried out in different angles but this paper reveals a new idea to enhance the performance of MultiLevel Inverter (MLI). An attempt is made to improve the performance of MLI and also to reduce the significant third harmonic energy by using amalgamation technique. A Trapezoidal Amalgamated Rectangular (TAR) reference signal is developed to study the performance of chosen five level cascaded MLI. To validate the developed technique, simulation and experimentation are carried out through MATLAB/SIMULINK and dSPACE respectively. Three different modulation strategies, Unipolar Amalgamated Phase Disposition (UAPD), Unipolar Amalgamated Phase Shift (UAPS) and Unipolar Amalgamated Carrier Overlapping (UACO) PWM methods are developed and implemented. Harmonic analyses are done for above amalgamated reference techniques which provide better results. The simulation and experimental results closely match with each other validating the strategies presented.